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Potassium & Digoxin

Mar 30, 2011 | By Ngozi Oguejiofo
Potassium & Digoxin
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The human body needs oxygen and other nutrients to work properly. These materials are delivered to all parts of the body by the pumping action of the heart, blood and blood vessels. When the heart is unable to pump out adequate amounts of blood to the body, heart failure occurs. Digoxin is a medication used to treat heart failure. Medications that affect serum levels of potassium are also used to treat heart failure.

Potassium

Potassium is found in food and in the body. In the body, it is an electrolyte that has the ability to conduct electricity. Ninety-eight percent of the potassium in the body is located inside the cells. The bloodstream -- outside the cells -- contains a small amount of potassium. This difference in concentration is important for processes such as stimulation of the nerves and muscle contraction to occur normally. A decrease or increase in the amounts of potassium in the bloodstream can cause problems such as abnormal heart rhythms.

Digoxin

Digoxin belongs to a class of medications called cardiac glycosides. In heart failure treatment, digoxin makes the heart pump with more force so that blood supply to the body can be more effective. Digoxin is able to do this because it inhibits the action of the enzyme that regulates entry of potassium, sodium and calcium into the heart's muscles. This increases the amount of calcium -- an electrolyte that stimulates stronger contraction of the heart's muscles -- inside the heart's cells, but reduces the level of potassium within these cells. This occurs because potassium moves out of the cells and into the bloodstream.

Digoxin Toxicity

The book "Pharmacology" by Pamela C. Champe, explains that digoxin toxicity is the most common adverse effect of digoxin. Use of digoxin as ordered by a physician or an overdose of the medication can cause digoxin toxicity. Initial symptoms of digoxin toxicity are nausea and loss of appetite. In severe cases of toxicity, visual disturbances such as seeing yellow lights and blurry vision occurs. Vomiting and cardiac arrhythmia are also signs of severe digoxin toxicity.

Relationship

"Blueprints Notes and Cases, Pharmacology," by Katherine Y. Yang, Larissa R. Graff and Aaron B. Caughey explains that low levels of potassium in the bloodstream -- a condition called hypokalemia -- increases the chances of digoxin toxicity because both digoxin and potassium have the same target sites in the heart. Therefore, in the presence of hypokalemia, digoxin will have more sites to bind to and this can then enhance it's effects. Also, in severe digoxin overdose, hyperkalemia or a higher than normal level of potassium in the bloodstream can occur. This is due to a large shift of potassium in the skeletal muscles to the bloodstream.

Considerations

Diuretics are medications used in heart failure treatment. They remove excess water from the body. Potassium wasting diuretics can cause hypokalemia because they promote loss of potassium along with removal of excess water. This can then increase a patient's chances of developing digoxin toxicity.

References

Article reviewed by Libby Swope Wiersema Last updated on: Mar 30, 2011

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